/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.solr.analysis;

import java.util.Map;
import java.io.IOException;

import org.apache.lucene.analysis.KeywordMarkerFilter;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.snowball.SnowballFilter;
import org.apache.solr.common.ResourceLoader;
import org.apache.solr.util.plugin.ResourceLoaderAware;
import org.tartarus.snowball.SnowballProgram;

/**
 * Factory for {@link SnowballFilter}, with configurable language
 * <p>
 * Note: Use of the "Lovins" stemmer is not recommended, as it is implemented
 * with reflection.
 * 
 * <pre class="prettyprint" >
 * &lt;fieldType name="text_snowballstem" class="solr.TextField" positionIncrementGap="100"&gt;
 *   &lt;analyzer&gt;
 *     &lt;tokenizer class="solr.StandardTokenizerFactory"/&gt;
 *     &lt;filter class="solr.LowerCaseFilterFactory"/&gt;
 *     &lt;filter class="solr.SnowballPorterFilterFactory" protected="protectedkeyword.txt" language="English"/&gt;
 *   &lt;/analyzer&gt;
 * &lt;/fieldType&gt;
 * </pre>
 * 
 * @version $Id: SnowballPorterFilterFactory.java 1074243 2011-02-24 18:07:16Z
 *          rmuir $
 */
public class SnowballPorterFilterFactory extends BaseTokenFilterFactory
		implements ResourceLoaderAware {
	public static final String PROTECTED_TOKENS = "protected";

	private String language = "English";
	private Class<?> stemClass;

	public void inform(ResourceLoader loader) {
		String wordFiles = args.get(PROTECTED_TOKENS);
		if (wordFiles != null) {
			try {
				protectedWords = getWordSet(loader, wordFiles, false);
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
	}

	private CharArraySet protectedWords = null;

	@Override
	public void init(Map<String, String> args) {
		super.init(args);
		final String cfgLanguage = args.get("language");
		if (cfgLanguage != null)
			language = cfgLanguage;

		try {
			stemClass = Class.forName("org.tartarus.snowball.ext." + language
					+ "Stemmer");
		} catch (ClassNotFoundException e) {
			throw new RuntimeException("Can't find class for stemmer language "
					+ language, e);
		}
	}

	public TokenFilter create(TokenStream input) {
		SnowballProgram program;
		try {
			program = (SnowballProgram) stemClass.newInstance();
		} catch (Exception e) {
			throw new RuntimeException(
					"Error instantiating stemmer for language " + language
							+ "from class " + stemClass, e);
		}

		if (protectedWords != null)
			input = new KeywordMarkerFilter(input, protectedWords);
		return new SnowballFilter(input, program);
	}
}
